The present invention relates to an exposure apparatus used for generating fine patterns for various products including semiconductor circuits (Ics), liquid crystal displays (LCDs) and the like, as well as to air-conditioning apparatus for use with such exposure apparatus. More particularly, the present invention relates to apparatus for effecting air-conditioning of a chamber which houses all or some of the components of an exposure apparatus for transferring a pattern formed on a mask onto a photosensitized substrate by exposure, including a light source, an illumination optical system, an exposure unit and others, in order to eliminate or minimize any harmful effects of impurities in the chamber.
A clean room used in fabrication of semiconductor devices is provided with an air purification system for removing particulate contaminants from the air in the room, and such air purification system typially uses high efficiency particulate air (HEPA) filters and/or ultra low penetration air (ULPA) filters. Various equipment and apparatus are used in the fabrication of semiconductor devices, among which exposure apparatus using ultraviolet (UV) light or deep-ultraviolet (DUV) light for exposure have been commonly used. In an exposure apparatus of this type, gaseous impurities in the surrounding atmosphere may undergo certain chemical and/or physical changes and form adhesive substances that tend to adhere to the surface of glass optical elements such as lenses and mirrors, resulting in blurring and/or reduced transmittance of the elements. For example, ammonium ions (NH4) and sulfur oxides (SOx), two typical, harmful gaseous impurities, form an adhesive layer of ammonium sulfate ((NH4)2SO4) on a surface of a glass optical element.
Thus, for long-term, continuous and effective operation of an exposure apparatus using a UV or DUV light source, it is required that the space along the light path of the light beam from the light source be filled with a gas having no sensitivity to UV or DUV radiation such as nitrogen and helium, or with an environmental gas (ambient air) having any harmful gaseous impurities removed therefrom. A known technique used for this purpose is to confine the space along the light path of the exposure light beam to an airtight chamber, and fill the chamber with a gas having no sensitivity to exposure radiation. The gas is supplied from a suitable gas supply device such as a gas cylinder or a gas storage tank. Another known technique used for this purpose is to supply ambient air outside the exposure apparatus to the illumination optical system in the exposure apparatus, after the air has been passed through an impurity-removing filter such as a chemical filter to remove any harmful gaseous impurities from the air.
Chemical filters can remove, unlike HEPA and ULPA filters, gaseous impurities from the environmental gas. Various chemical filters are commonly used, including those using fibrous or granulate activated carbon, those utilizing ion exchange reaction provided by various ion exchange resins, and those using fibrous activated carbon with some sort of agent added. Examples of chemical filters utilizing an ion exchange reaction are products bearing a trademark xe2x80x9cEPIXxe2x80x9d available from Ebara Corporation in Japan. Examples of chemical filters using fibrous activated carbon with some sort of agent added are products bearing a trademark xe2x80x9cCLEAN SORBxe2x80x9d available from Kondo Kogyo Co, Ltd. in Japan.
Various resists are used in photolithographic process in order to form patterns on a substrate, among which chemically sensitized resists have become common recently. In general, chemically sensitized resists consist of a resin, a photosensitive acid generator (PAG), and either a dissolution promotor (for positive resists) or a cross-linking agent (for negative resists). When exposed to exposure radiation, the photosensitive acid generator generates an acid. During the post-exposure baking process, the acid acts as a catalyst. In the case of a positive resist, the catalyst increases the activity of the dissolution promotor to break cross-links between the polymer molecules. In the case of a negative resist, the catalyst increases the activity of the cross-linking agent to form cross-links between the polymer molecules. In both cases, a pattern is formed with the aid of the catalyst during the following development process, in which a positive resist using a dissolution promotor forms positive patterns while a negative resist using a cross-linking agent forms negative patterns on the substrate. Examples of the positive chemically amplified resists are products bearing a trademark xe2x80x9cFH-EX1xe2x80x9d available from Fuji-Hunt Corporation. Examples of negative chemically amplified resists are products bearing a trademark xe2x80x9cXPxe2x80x9d available from Shipray Corporation.
When a chemically sensitized resist is used, some basic gaseous impurities (ammonia and amines, for example) in the local atmosphere around the substrate and acid generated from the photosensitive acid generator may cause a neutralization reaction during the time interval between exposure to post-exposure baking, resulting in reduced sensitivity. Further, in the case of a positive resist this also results in the formation of a dissolution-resistant surface layer, which may affect the pattern transfer process. A commonly used technique used to avoid the adverse effects of such gaseous impurities is to fill the process atmosphere for the sequence of processes from the application process of chemically sensitized resist on a substrate (or from the exposure process of a substrate applied with chemically amplified resist) to post-exposure baking with a clean gas containing no impurities.
More specifically, where this technique is used to avoid adverse effects of gaseous impurities, a chamber is used to house the entire exposure apparatus or at least a critical part thereof. The chamber has an air inlet through which ambient air is introduced into the chamber. The air inlet is provided with a gaseous-impurity-removing device, such as a chemical filter, for preventing any gaseous impurities from entering the chamber. In addition, the chamber is provided with a second chemical filter for removing any gaseous impurities from a gas stream recirculating in the chamber.
However, the above prior art technique suffers from several problems as described below. First, a problem arises relating to the filters used. Chemical filters are commonly used as gaseous-impurity-removing devices. The impurity removal efficiency of a chemical filter, however, tends to gradually decrease as more gaseous impurities are caught and removed by the filter. The rate of decrease in the impurity removal efficiency depends on several factors including the concentrations of the gaseous impurities contained in the environmental gas in which the chemical filter is used, as well as the humidity of the environmental gas. An even rate of operation of the semiconductor device factory equipped with an exposure apparatus may cause significant changes in the concentrations of the gaseous impurities in the environmental air of the exposure apparatus.
An impurity-removing filter element has to be replaced when its impurity removal efficiency has dropped below a minimum acceptable level. Typically, the life of a filter element is defined as the point of time when its impurity removal efficiency has decreased to a predetermined threshold level. However, the rate of degradation of a filter element depends on environmental conditions as described above, and impurity concentrations in different environments of respective filter elements are quite different from each other, so that it is difficult to predict with precision when a particular filter element has reached the end of its effective life.
In order to determine the impurity removal efficiency of a filter element used with an exposure apparatus, it is required to set a gas-concentration-measuring device on the exposure apparatus for measurement at regular intervals. However, this may result in an increase in the nonworking time of the exposure apparatus because of the necessary time for setting and removal of the gas-concentration-measuring device on and away from the exposure apparatus as well as of the time for the concentration measurement itself. Further, where a plurality of exposure apparatus are disposed in a single clean room, the impurity concentration in the environment of one exposure apparatus may be quite different from that of another exposure apparatus, resulting in different rates of degradation of the filter elements used with them. Therefore, for the plurality of exposure apparatus, the impurity concentrations have to be measured individually, which results in a troublesome measurement work and may often result in a reduced productivity.
In addition, for an exposure apparatus using a chemical filter for introducing ambient air into the apparatus through the filter, if an abrupt and significant increase occurs in the gaseous impurity concentration in the ambient air outside the apparatus, then the chemical filter may not completely remove gaseous impurities from the air stream being introduced in the apparatus, resulting in possible contamination inside the apparatus and/or the formation of a dissolution-resistant layer on the surface of the chemically sensitized resist layer on the substrate being processed in the apparatus.
The above prior art technique also suffers from another problem relating to the integrity of the airtightness of the chamber which houses the entire exposure apparatus or a part thereof. The chamber is provided with an gas-delivering fan for producing a gas stream recirculating in the chamber, with the result that a negative pressure area is generated in the chamber upstream of the gas-delivering fan. Further, the chamber has an air inlet through which the ambient air is introduced into the chamber by means of suction produced by the negative pressure area near the air inlet. The chamber has a wall composed of panels, which joined to each other in such a way as to ensure airtightness of the chamber. In particular, such a portion of the chamber wall that is around the negative pressure area must be kept airtight, and the panels constituting that wall portion are typically joined with each other with appropriate sealant (silicone sealant, for example) applied to the joints between the panels. The airtightness is required because all the air introduced into the chamber must pass through the air inlet, i.e., no air must not be allowed to leak into the chamber through any other path such as a defect in a joint between two panels.
However,the airtightness of the chamber may be lost due to degradation or a failure of the sealant applied to the joints between the panels, such as chipping and cracking of the sealant. If the sealant suffers from such chips and/or cracks that are very small or hidden behind some other components of the exposure apparatus, the operator of the apparatus can not locate such defects in the sealant. This may allow leakage of ambient air containing impurities into the chamber, resulting in accelerated degradation of the gaseous-impurity-removing filter used in the chamber and/or contamination inside the chamber.
It is also known that a problem arises due to moisture contained in the gas in the chamber, as follows. Most of the amount of impurities contained in the ambient air is adsorbed on the surface of dust and water particulates floating in the ambient air. The ambient air in a building of a typical semiconductor device factory as well as the gas in the local atmosphere in the chamber of an exposure apparatus equipped in such factory has relatively large particles already removed therefrom by some sort of particulate filters such as ULPA filters. On the other hand, the humidity of such ambient air or gas is maintained at a level typically in the range of 30 to 50%. Any humidity level in this range allows the existence of water particulates floating in the air or gas, to which ions and other impurities are adsorbed, resulting in possible contamination inside the exposure apparatus.
Hexamethyldisilazane (HMDS), which is commonly used in semiconductor processes, tends to react with moisture in air or gas to undergo hydrolysis into trimethylsilanol and ammonia, as follows. 
The resultant ammonia may react with the acid generated by PAG in the resist, which reaction affects the image formation properties of the resist. It is also known that some sort of amines, such as NMP, can affect the image formation properties of resists. In addition, it is very likely that various other matters which may react with moisture in air or gas to form harmful impurities are used in semiconductor processes.
Further, even moisture in ambient air itself may affect the image formation properties of resists. However, no special consideration has been given to humidity so far.
It is also noted in this relation that the complete removal or elimination of the moisture from the air in a semiconductor device factory or from the gas in the exposure apparatus equipped in the factory tends to cause a static discharge problem which may affect the exposure apparatus.
Often, either helium gas or nitrogen gas generated by vaporization of liquid nitrogen is used as a dry gas to be filled in the exposure apparatus. In such a case, because the exposure apparatus has to be continuously supplied with the dry gas in order to keep the inside of the apparatus filled with the gas, considerable consumption of the supplied gas arises, resulting in a large expenditure and even in a possible decrease in oxygen concentration in the environmental air in the factory, which may put workers at risk in the factory.
A further known problem arises in relation to the chemical filter elements which have to be housed in respective boxes and disposed at various places, such as inside the exposure apparatus, around the apparatus and/or in the flow path of the supplied gas. This problem is described with reference to FIG. 26 of the accompanying drawings.
FIG. 26 is a schematic representation showing a typical prior art exposure apparatus. The exposure apparatus has an exposure unit comprising a light source 200, a first mirror 201a, an illumination optical system 202, a second mirror 201b, a projection lens 203 and an XY-stage 204. The exposure unit serves to transfer a pattern formed on the reticle 205 onto a photosensitized substrate 207 placed on the XY-stage 204. The exposure unit is housed in a chamber 208.
The air in the chamber 208 is temperature-controlled by an air-conditioning apparatus 220, and delivered through an impurity-removing unit including a chemical filter 209 and a particulate filter 210 such as a HEPA filter. The filters 209 and 210 have respective filter boxes in which filter elements are housed. The filters 209 and 210 are disposed one after the other along the flow path of the air stream passing therethrough. The air stream flows out of the impurity-removing unit into the local atmosphere around the exposure unit, and then passes through a return path 211 and again is temperature-controlled by the air-conditioning apparatus 220 so as to recirculate in the chamber 208. The air-conditioning apparatus 220 includes components such as a temperature regulator 221 and a gas-delivering fan 222, which are connected through ducts 223a and 223b with the chamber 208. The return path 211 is upstream of the air-conditioning apparatus 220 and defines therein a negative pressure area with respect to the ambient air pressure outside the chamber 208. During the operation of the exposure apparatus, certain amounts of air repetitively leak out of the chamber from the local atmosphere around the exposure unit, and the corresponding amounts of air are repetitivey drawn into the chamber 208 through an air inlet 212 and an impurity-removing filter element 213 under the infuluence of the negative pressure in the above mentioned area.
As shown, an gaseous-impurity-removing filter, such as a chemical filter, comprises a filter element and a filter box for housing the filter element. The filter box is bulky and requires a relatively large installation space. In the case where an filter boxe is disposed in the exposure apparatus, the space in the apparatus available for other purposes is reduced and/or the exposure apparatus must have the larger volume for the filter box.
In view of the foregoing, it is a first object of the present invention to provide an exposure apparatus, in which end-of-life of a chemical filter element used in the exposure apparatus may be determined with precision, maintenance services such as replacement and/or cleaning of the chemical filter element may be performed in good time, and impurities in ambient air may be effectively prevented from entering the apparatus even when the impurity concentration in ambient air in the environment of the apparatus has made an abrupt and significant increase during the operation of the apparatus.
It is a second object of the present invention to provide an exposure apparatus with a chamber, in which any failure of the integrity of the airtightness of the chamber (which may be caused by some defect or another) will never lead to a leakage of the ambient air into the chamber through such defect, which could otherwise result in an inconvenience increase in the gaseous impurity concentration in the chamber.
It is a third object of the present invention to provide an exposure apparatus, in which a portion of the apparatus that is sensitive to impurities in ambient air may be placed in a local atmosphere of dehumidified air.
It is a fourth object of the present invention to miniaturize an exposure apparatus by minimizing the space occupied by impurity-removing filter(s) used.
According to a first embodiment of the present invention for achieving the first object described above, there is provided an exposure apparatus for transferring a pattern formed on a mask onto a photosensitized substrate by exposure, comprising: a light source for emitting a light beam having a wavelength falling in a range from ultraviolet to deep ultraviolet radiation; an illumination optical system for directing the light beam from the light source into the mask; an exposure unit for making exposure of a photosensitized substrate in order to transfer the pattern formed on the mask onto the photosensitized substrate; a chamber for housing at least a part of the exposure apparatus; an ambient air introducing unit for introducing ambient air into the chamber; an impurity-removing filter for removing gaseous impurities from one of the gas streams including a stream of ambient air being introduced into the chamber and a gas stream recirculating in the chamber; a pair of impurity-concentration-measuring devices disposed upstream and downstream, respectively, of the impurity-removing filter; and a filter end-of-life determination device for determining end-of-life of the impurity-removing filter based on measurements from the impurity-concentration-measuring device disposed upstream of the impurity-removing filter and measurements from the impurity-concentration-measuring device disposed downstream of the impurity-removing filter.
In the exposure apparatus according to the first embodiment of the present invention for achieving the first object described above, the impurity-removing filter may be preferably arranged for removing gaseous impurities from the stream of ambient air being introduced into the chamber, and wherein the exposure apparatus may preferably further comprise a control device for stopping operation of the ambient air introducing unit when the impurity-concentration-measuring device disposed upstream of the impurity-removing filter has indicated a gaseous impurity concentration above a predetermined level.
According to a second embodiment of the present invention for achieving the first object described above, there is provided an exposure apparatus for transferring a pattern formed on a mask onto a photosensitized substrate by exposure, comprising: a light source for emitting a light beam having a wavelength falling in a range from ultraviolet to deep ultraviolet radiations; an illumination optical system for directing the light beam from the light source into the mask; an exposure unit for making exposure of a photosensitized substrate in order to transfer the pattern formed on the mask onto the photosensitized substrate; a chamber for housing at least a part of the exposure apparatus; an ambient air introducing unit for introducing ambient air into the chamber; an impurity-removing filter for removing gaseous impurities from a stream of ambient air being introduced into the chamber; an impurity-concentration-measuring device disposed upstream of the ambient air introducing unit; and a control device for stopping operation of the ambient air introducing unit when the impurity-concentration-measuring device has indicated a gaseous impurity concentration above a predetermined level.
In the first and second embodiments of the present invention for achieving the first object described above, the impurity-concentration-measuring device may measure concentrations of at least one of impurities including ammonium ion (NH4+) and sulfate ion (SO42xe2x88x92), or may measure concentration of organosilicon compounds, such as siloxanes.
According to a third embodiment of the present invention for achieving the second object described above, there is provided an exposure apparatus for transferring a pattern formed on a mask onto a photosensitized substrate by exposure, comprising: a light source for emitting a light beam having a wavelength falling in a range from ultraviolet to deep ultraviolet radiations; an illumination optical system for directing the light beam from the light source into the mask; an exposure unit for making exposure of a photosensitized substrate in order to transfer the pattern formed on the mask onto the photosensitized substrate; a chamber for housing at least a part of the exposure apparatus, the chamber having an air inlet for introducing ambient air into the chamber; a gas-recirculating device disposed in the chamber for producing a gas stream recirculating in the chamber while generating a negative pressure area near the air inlet; and an airtightness-integrity-sensing device for sensing integrity of airtightness of the chamber around the negative pressure area.
In the exposure apparatus according to the third embodiment of the present invention for achieving the second object described above, it may be preferable that the exposure apparatus further comprises a control device for taking, when a failure of integrity of airtightness of the chamber is detected by means of the airtightness-integrity-sensing device, at least one of actions including providing an alarm of a failure of integrity of airtightness and stopping operation of the gas-recirculating device.
This may effectively prevent an accelerated degradation of any impurity-removing filter disposed in the chamber.
Further, in the exposure apparatus according to the third embodiment of the present invention for achieving the second object described above, the airtightness-integrity-sensing device may comprise a differential pressure gauge or an anemometer. the anemometer may be disposed in the air inlet of the chamber. Both of the differential pressure gauge and the anemometer may be used in parallel. If a failure or defect occurs in the sealant used for the chamber, the ambient air leaks into the chamber through the defect, resulting in the corresponding change in the flow rate of the air stream being introduced through the air inlet into the chamber. Thus, the integrity of the airtightness of the chamber may be administrated by sensing the change in the flow rate.
It is preferable that a first gaseous-impurity-removing device is disposed in the air inlet of the chamber and a second gaseous-impurity-removing device is disposed in a flow path of the gas stream recirculating in the chamber. Each of the gaseous-impurity-removing devices may comprise a chemical filter. Chemical filters can remove, unlike HEPA and ULPA filters, gaseous impurities from the environmental gas. Various chemical filters are commonly used including those using fibrous or granulate activated carbon, those utilizing ion exchange reaction provided by various ion exchange resins, those using fibrous activated carbon with some sort of agent added. Examples of the chemical filters utilizing ion exchange reaction are the products having a trademark xe2x80x9cEPIXxe2x80x9d available from Ebara Corporation in Japan. Examples of the chemical filters using fibrous activated carbon with some sort of agent added are the products bearing a trademark xe2x80x9cCLEAN SORBxe2x80x9d available from Kondo Kogyo Co, Ltd. in Japan.
This arrangement may be also used to make an inspection of the sealing work of the chamber at the completion of the chamber, and in particular an inspection of the sealant applied to the joints between panels constituting the chamber wall.
According to a fourth embodiment of the present invention for achieving the third object described above, there is provided an exposure apparatus for transferring a pattern formed on a mask onto a photosensitized substrate by exposure, comprising: a light source for emitting a light beam having a wavelength falling in a range from ultraviolet to deep ultraviolet radiations; an illumination optical system for directing the light beam from the light source into the mask; an exposure unit for making exposure of a photosensitized substrate in order to transfer the pattern formed on the mask onto the photosensitized substrate; a chamber for housing at least a part of the exposure apparatus; and a gas supply device for supplying dehumidified gas to a desired area around the exposure apparatus.
However, when the moisture in an semiconductor device factory or in an exposure apparatus is completely eliminated, electrostatic discharges are likely to occur. Semiconductor devices are subject to failures caused by electrostatic discharge, such as destruction of the chips and functional failures of circuits in the chips, so that any electrostatic charge may result in a reduced yield of the semiconductor devices. On the other hand, filing all the area in the apparatus all the time with some sort of dry gas is very costly.
Therefore, in this embodiment, it is preferable that only the local atmosphere around the photosensitized substrate and/or the local atmosphere around the illumination optical system are/is filled with the dehumidified gas. Further, the dehumidified gas may preferably comprise dehumidified ambient air. One typical method of dehumidifying the ambient air is to cool an amount of the ambient air to a very low temperature about xe2x88x9230 to xe2x88x9240xc2x0 C. so as to freeze any moisture in the air into ice and remove from the air. A sensing device for sensing the existence of the photosensitized substrate may be provided and the supply of the dehumidified gas may be controlled depending on presence/absence of the photosensitized substrate. The dehumidified gas may be generated by causing a gas stream to pass through a gaseous-impurity-removing filter and then through a dehumidifier. In the case where a plurality of exposure apparatuses are equipped in a factory, the dehumidifier for generating the dehumidified gas may comprise a plurality of dehumidifying unit each provided for one of the exposure apparatuses, or may comprise a single dehumidifying unit common to all the exposure apparatuses for generating the dehumidified air and distributing it to them.
In order to avoid any electrostatic discharge, it is preferable that an antistatic device is provided for such parts that are likely to accumulate electrostatic charge by friction, such as the parts which come into contact with the photosensitized substrate in a local atmosphere in the area to which the dehumidified gas is supplied. The antistatic device may be a device for grounding such parts.
In this arrangement, only selected area(s) will undergo dehumidification, so that the dehumidification can be effectively performed and the reduction in nonuniformity among the resist images and the reduction in the contamination of the optical elements can be achieved because any contamination by the impurities conveyed by water particulates or by the moisture itself is eliminated.
Further, in the case where purified dehumidified gas is generated by causing a gas stream to pass through a gaseous-impurity-removing filter and then through a dehumidifier, any contamination of the apparatus may be reduced more effectively. Chemical filters be used as the gaseous-impurity-removing filter, and it can remove, unlike HEPA and UL,PA filters, gaseous impurities from the environmental gas. Various chemical filters are commonly used including those using fibrous or granulate activated carbon, those utilizing ion exchange reaction provided by various ion exchange resins, those using fibrous activated carbon with some sort of agent added. Examples of the chemical filters utilizing ion exchange reaction are products bearing a trademark xe2x80x9cEPIXxe2x80x9d available from Ebara Corporation in Japan. Examples of the chemical filters using fibrous activated carbon with some sort of agent added are products bearing a trademark xe2x80x9cCLEAN SORBxe2x80x9d available from Kondo Kogyo Co, Ltd. in Japan. Gaseous impurities to be removed by the chemical filter include SO42xe2x88x92, NH4+, organosilicom compounds, trimethylsilanol, N-methyl-2-pyrrolidon and others.
In addition, the supplied dehumidified gas may typically comprise dehumidified ambient air, with the result that a possible leakage of the dehumidified gas into a factory room will never risk the workers in the room. This also provides an advantage that the use of such dehumidified gas is less costly than the use of nitrogen or helium gas.
According to a fifth embodiment of the present invention for achieving the fourth object described above, there is provided an air-conditioning apparatus for removing impurities from gas, adapted for effecting air-conditioning to a semiconductor device factory and/or an exposure apparatus, comprising: a body housing; a gas supply duct housed in the body housing; and an impurity-removing filter element disposed inside the gas supply duct.
According to a sixth embodiment of the present invention for achieving the fourth object described above, there is provided an exposure apparatus for transferring a pattern formed on a mask onto a photosensitized substrate by exposure, comprising: a light source for emitting a light beam having a wavelength falling in a range from ultraviolet to deep ultraviolet radiations; an illumination optical system for directing the light beam from the light source into a mask; an exposure unit for exposing a photosensitized substrate in order to transfer the pattern formed on the mask onto the photosensitized substrate; a chamber for housing at Least a part of the exposure apparatus; and an air-conditioning apparatus for effecting conditioning of gas in the chamber, said air-conditioning apparatus being disposed outside the chamber and comprising a body housing, a gas supply duct housed in the body housing and an impurity-removing filter element disposed inside the gas supply duct.
The impurity-removing filter element may comprise a hollow cylindrical body or may comprise a bellows wall. Further, the impurity-removing filter element may be so supported by a support member as to be kept out of contact with an inner wall of the gas supply duct. The duct is bendable with the impurity-removing filter element contained therein. A filter element having a hollow cylindrical body has a relatively large filtering surface area and is effective to reduce the pressure loss across the filter element.
The impurity-removing filter element may be a gaseous-impurity-removing element, or may be a combined filter element comprising a gaseous-impurity-removing filter element and a particulate filter element. Further, the gaseous-impurity-removing filter element may comprise a chemical filter using some sort of ion exchange resin, or a chemical filter using fibrous activated carbon with some sort of agent added, for removing gaseous impurities such as ammonia, basic amines, sulfate ion, N-methyl-2-pyrrolidon, trimethylsilanol and others. The particulate filter may comprise a HEPA filter or an ULPA filter.
According to this embodiment, an impurity-removing filter element may be disposed in an air-conditioning apparatus at a space inside an existing duct, occupying no other space which may be utilized for other purposes. An air-conditioning apparatus according to this embodiment may be used with an exposure apparatus or with a clean room.